Crops and Methods for Soil Improvement

by Alva Agee

Acquaintance with Terms.—The hesitation of many users of commercial fertilizer to master the few technical terms used in analyses of the goods, for which over one hundred million dollars annually are expended in this country, is to be deplored. The number of the materials available for any large use as sources of plant-food in a commercial fertilizer is small, and something of their characteristics should be known. Every farmer should have a working knowledge of these materials—their sources, the percentage of plant-food carried by them, and their probable availability. He should know in a general way their advantages and disadvantages in comparison with each other.

Nitrate of Soda.—One of the best carriers of nitrogen is nitrate of soda, which is imported from Chili, South America, where great beds exist. The most of the impurities are removed, and the nitrate of soda comes to us in bags holding 200 pounds, and looks much like discolored salt. It is easily soluble in water, and usually contains a little over 15 per cent of nitrogen, which is in a very available form. Its immediate availability brings it into use by gardeners and truckers, and it is an excellent source of nitrogen for grass fertilizers to be used in the early spring. It was formerly advised that nitrate of soda should not form part of a fertilizer for use before plant-roots had filled the ground, its high availability being supposed to lead to heavy loss by leaching. The Pennsylvania experiment station uses it as its sole source of nitrogen in fertilizers for staple crops on its 900 acres of farm land. It is effective in fertilizers for corn, wheat, potatoes, and grass, as well as for special crops.

The warnings regarding loss by leaching should not be disregarded, however. If the price of nitrogen in an organic form were as low as it has been in nitrate of soda, and if the soils of the Pennsylvania station farms were sandy, the use of nitrate of soda as the sole carrier of nitrogen would be inadvisable. The only fact of consequence is that the danger of loss has been over-stated, turning some farmers away from the use of a good and relatively cheap carrier of nitrogen.

Sulphate of Ammonia.—This is a by-product in the manufacture of coke and also of illuminating gas. Hunt estimates that the amount of nitrogen lost annually in Pennsylvania's coke industry would be sufficient, if recovered by proper type of ovens, to furnish every acre of land under cultivation in the state with four fifths of all the nitrogen needed to keep it in a maximum state of fertility.

Sulphate of ammonia contains about 20 per cent of nitrogen, which is in a quite available form. It has a tendency to exhaust the lime in the soil, producing an acid condition. Some plats in the fertilizer experiment at the Pennsylvania station have received their nitrogen in the form of sulphate of ammonia for 30 years, and are now in such acid condition that no crops thrive upon them. The corrective, of course, is lime, and if ammonium sulphate were somewhat lower in price, its use would be profitable, justifying cost of correction of acidity if it should occur. It is used by manufacturers of commercial fertilizers, and is well adapted to mixtures on account of its physical condition.

Dried Blood.—There is no more satisfactory source of organic nitrogen than dried blood of high grade. The best blood, red in color, contains nearly as much nitrogen as nitrate of soda, running from 13 to 15 per cent. The nitrogen is not as quickly available as that in the nitrate, but is more so than that in any other form of organic nitrogen. One would rarely go amiss in the purchase of dried blood as a carrier of nitrogen if the price were relatively as low as in the case of nitrate of soda, but he should not let any prejudice in favor of animal origin of fertilizers lead him to pay an excessive price per pound for the nitrogen contained in it. Such a prejudice has caused the nitrogen in a good red blood to sell for one half more per pound than in nitrate of soda, and it is not a good purchase on that basis.

The lower grades of dried blood on the market contain as low as 6 per cent of nitrogen, and the animal refuse put into it gives it a content of a few per cent of phosphoric acid. This black blood is very variable in composition, and should always be accompanied by a guaranteed analysis.

Tankage.—The waste from the slaughter of animals goes into a product called tankage. The refuse is cooked for removal of the fat, and then ground. It may run high in nitrogen on account of the amount of meat in the mixture, and it may be low in nitrogen and very high in phosphoric acid by reason of the large amount of bone in the mixture. Only a guarantee of analysis affords safety to the buyer. It is a relatively slow and good fertilizer, and is used usually in connection with forms of plant-food that are more quickly available.

Fish.—Near the Atlantic coast a large quantity of ground fish, after the extraction of oil, is used as a fertilizer, but the cost of the nitrogen and phosphoric acid in this carrier is relatively too high to justify its free use. Like dried blood, its organic character gains for it a popularity that does not have full justification in fact.

Animal Bone.—The original source of phosphoric acid as a fertilizer was animal bone, just as hard-wood, unleached ashes were the source of potash. The organic character of the animal bone made it appear more truly a manure than could any rock or other inorganic substance. There is no more satisfactory source of phosphoric acid than animal bone, and if it were in full supply for the needs of soils, there would be little occasion to discuss the merits of rock-phosphate and other similar materials. The supply is a small fraction of the need. If all animal bone were carefully saved and returned to the land that produced all of our animals, it would return to the soil only what those animals carried away in their bones, and that is indeed a small fraction of all the draft our crops make upon the soil's supply of this one substance. Some of the best animal bone goes into the manufacture of articles that never contribute anything to the soil, and there are other sources of loss. The supply of phosphoric acid from bone is too small, when compared with the land's need, to deserve more than a small fraction of the consideration it receives by users of commercial fertilizers.